A melt after reaction in a reactor for polymerization or polycondensation is extruded out from the reactor, for example, as strands or a sheet, and cooled and solidified in a liquid such as water or the like, and thereafter pelletized with a pelletizer to give resin pellets.
In the case where the melt is a crystalline resin, the resin is uncrystallized just after pelletized with a pelletizer, and therefore has a problem in that the resin pellets may block to each other (for example, bonding or caking of resin pellets to each other) in a liquid such as water or the like.
A so-called soft resin also has a problem in that, when formed into pellets, the resin pellets may block to each other in a liquid.
As a method for preventing resin pellets from blocking to each other and for increasing the degree of crystallization of the resin in the form of pellets, there has been proposed a method for producing pellets of a crystalline polymer (for example, an aromatic copolyester, an aliphatic copolyester, etc.), wherein a melt of a crystalline polymer is extruded out as strands or a sheet, cooled and solidified, and thereafter pelletized with a pelletizer, and the resultant pellets in an uncrystallized state are mixed with pellets of the crystalline polymer that has been separately processed to have a degree of crystallization of 5% or more, and these are treated (for example, see PTL 1).
However, in the production method for crystalline polymer pellets mentioned above, pellets of a crystalline polymer that has been separately processed to have a degree of crystallization of 5% or more must be prepared, and further, the method requires a supply line for supplying the pellets of the crystalline polymer having a high degree of crystallization to the pellets of the uncrystallized polymer, and consequently, and therefore has a problem in that the production steps are complicated.